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About Enviroweather's Cherry Leaf Spot Report

By Bill Shane, MSU Extension

More information on cherry leaf spot at IPM Resources

About the model:

Infection is predicted with the table by Eisensmith and Jones (Table 1), which uses leaf wetness duration and air temperature data. In the model, a wetting period is initiated when rain begins. The wetting period ends when the relative humidity drops below 90% and the leaf wetness sensor is dry, and this is followed by 8 consecutive hours of dryness (i.e., no rain, relative humidity < 90%, and leaf wetness sensors read "dry"). If leaves again become wet within 8 hours, the wetting period continues.

A wetting period may result in no infection or infection by the cherry leafspot pathogen.

Use of the model:

The cherry leaf spot model can be used as a guide to determine the need for eradicative sprays if a protectant coverage was weak during a rain episode. The model should not be used as a routine guide for eradicative spray applications-a protectant spray program is the most reliable approach for control of cherry leaf spot. The model is useful for comparing predicted leaf spot infection activity between years.

 

Table 1. Approximate number of hours of wetting period required for conidial infection by the cherry leaf spot fungus at various air temperatures.
Temperature (F)Wetting period (hr)
81 or warmer 28
80 21
79 18
78 16
77 14
76 12
75 11
74 9
73 8
72 7
71 7
70 6
69 6
63 - 68 5
62 6
61 6
60 7
59 7
58 8
57 9
56 10
55 11
54 12
53 14
52 15
51 17
50 19
49 20
48 23
47 25
46 28

 

References:

  • Eisensmith, S. P. and A. L Jones. 1981. A model for detecting infection periods of Coccomyces hiemalis on sour cherry. Phytopathology.71:728-732.
  • Jones, A. L. and T. B. Sutton. 1996. Diseases of tree fruits in the east. Northcentral Regional Bulletin 45, Michigan State University
  • More information on cherry leaf spot at IPM Resources

 

  • MSU Extension
  • Michigan State University Ag Bio Research
  • Project Greeen